Is there a link between land and soil degradation and climate change? A new book from Philip and Freya Mulvey reveals the profound connection between these two.
Phil Mulvey is a fellow soil scientist and CPSS while his daughter Freya, is a lawyer with an interest in environmental law and policy.
Ground Breaking discusses the role of healthy, organic matter-rich soil and native vegetation (grasses, shrubs and trees) in the small water cycle and the relationship between the small water cycle and rainfall.
Citing two decades of research into rainfall differences on either side of Australia’s rabbit-proof fence – where land use on one side is predominantly cropping and on the other is predominantly grazing under native vegetation – the authors make the connection between latent heat and sensible (i.e. what you can feel) heat.
Incoming solar radiation is converted to one of two types of heat, latent and sensible. Latent heat promotes phase change of materials such as snow to water, or water to water vapour. Sensible heat is heat that is added or removed from a system in which there is no phase change, only a change in temperature.
Where native vegetation covers the ground, incoming solar radiation that is not reflected is converted to 75% latent heat and less than 20% is converted to sensible heat. Latent heat sees a phase change via evapotranspiration and is inherently cooling. In contrast, bare ground or ground with very low groundcover (e.g. crop fallow) produces 20% latent heat and 75% sensible heat.
Local increases in sensible heat generated by bare ground or ground with low groundcover previously rose to the upper stratosphere where its energy dissipated harmlessly. However, substantial increases in greenhouse gases (GHGs) since the industrial revolution have created the ‘greenhouse effect’ and trap a significant proportion of sensible heat. The increase in GHGs has paralleled rates of land clearing and expansion of cropping land unrivalled in human history. The generation of unprecedented levels of sensible heat from land surfaces is therefore a powerful driver of climate change, but its role in climate change mitigation scarcely rates a mention.
The authors highlight the failure of the recent review of Australia’s Environment Protection and Biodiversity Conservation (EPBC) Act 1999 to acknowledge the importance of soil or consider its role and management in achieving environmental protection and biodiversity conservation – their submission to the interim report on the EPBC Act fell on deaf ears.
Ground Breaking represents a significant contribution to the climate change debate, linking healthy organic matter-rich soils and diverse vegetation to the small and large water cycles and the rainfall that sustains us all.